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Title: Mobility transition at grain boundaries in two-step sintered 8 mol% yttria-stabilized zirconia

 [1]; ORCiD logo [1]
  1. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia Pennsylvania
Publication Date:
Sponsoring Org.:
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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of the American Ceramic Society
Additional Journal Information:
Journal Volume: 101; Journal Issue: 5; Related Information: CHORUS Timestamp: 2018-03-02 06:11:49; Journal ID: ISSN 0002-7820
Country of Publication:
United States

Citation Formats

Dong, Yanhao, and Chen, I-Wei. Mobility transition at grain boundaries in two-step sintered 8 mol% yttria-stabilized zirconia. United States: N. p., 2017. Web. doi:10.1111/jace.15362.
Dong, Yanhao, & Chen, I-Wei. Mobility transition at grain boundaries in two-step sintered 8 mol% yttria-stabilized zirconia. United States. doi:10.1111/jace.15362.
Dong, Yanhao, and Chen, I-Wei. Mon . "Mobility transition at grain boundaries in two-step sintered 8 mol% yttria-stabilized zirconia". United States. doi:10.1111/jace.15362.
title = {Mobility transition at grain boundaries in two-step sintered 8 mol% yttria-stabilized zirconia},
author = {Dong, Yanhao and Chen, I-Wei},
abstractNote = {},
doi = {10.1111/jace.15362},
journal = {Journal of the American Ceramic Society},
number = 5,
volume = 101,
place = {United States},
year = {Mon Dec 11 00:00:00 EST 2017},
month = {Mon Dec 11 00:00:00 EST 2017}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on December 11, 2018
Publisher's Accepted Manuscript

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  • Amorphous silicate grain boundary phases of varying chemistry and amounts were added to 3Y-TZP in order to determine their influence on the superplastic behavior between 1,200 and 1,300C and on the room-temperature mechanical properties. Strain rate enhancement at high temperatures was observed in 3Y-TZP containing a glassy grain boundary phase, even with as little as 0.1 wt% glass. Strain rate enhancement was greatest in 3Y-TZP with 5 wt% glass, but the room-temperature hardness, elastic modulus, and fracture toughness were degraded. The addition of glassy grain boundary phases did not significantly affect the stress exponent of 3Y-TZP, but did lower themore » activation energy for superplastic flow. Strain rate enhancement was highest in samples containing the grain boundary phase with the highest solubility for Y[sub 2]O[sub 3] and ZrO[sub 2], but the strain rate did not scale inversely with the viscosity of the silicae phases. Grain boundary sliding accommodated by diffusional creep controlled by an interface reaction is proposed as the mechanism for superplastic deformation in 3Y-TZP with and without glassy grain boundary phases.« less
  • In this study, 8 mol % yttria stabilized zirconia (YSZ) + La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSM) composite electrodes with addition of various amounts of YSZ were prepared on YSZ plates by a screen-printing method. The electrodes were then examined by scanning electron microscopy (SEM) and studied by ac impedance, cyclic voltammetry, and potential step as well as a polarization technique. For the oxygen reduction reaction on the pure LSM electrode, the dissociative adsorption of oxygen on the LSM surface and the transfer of oxygen ions from the triple-phase boundary (TPB) to the YSZ electrolyte lattice were found to be twomore » comparable rate-determining steps. The electrochemical resistance of the former step was proportional to the {minus}0.5 power of p{sub O{sub 2}}, with a high activation energy of {approximately}2.0 eV. The electrochemical resistance of the latter step was found to be independent of p{sub O{sub 2}} with a low activation energy of {approximately}1.0 eV. With addition of YSZ to the LSM electrode, the electrochemical activity was improved substantially with much lower electrochemical resistances for both steps. Furthermore, the dissociative adsorption of oxygen became less rate determining on the electrode with more YSZ addition. It was found that the transfer of oxygen ion was the only rate-determining step on the 40% YSZ + LSM electrode. The improvement in the electrochemical performance with addition of YSZ was found mainly due to the spatial enlargement of the TPB area, which increased the electrochemically active sites for the oxygen adsorption and charge-transfer reaction.« less
  • Grain-boundary plane, misorientation angle, grain size, and grain-boundary energy distributions were quantified using electron backscatter diffraction data for dense polycrystalline yttria-stabilized zirconia, to understand interfacial crystallography in solid oxide fuel cells. Tape-cast samples were sintered at 14501C for 4 h and annealed for at least 100 h between 8001C and 16501C. Distributions obtained from both three-dimensional (3D) reconstructions and stereological analyses of 2D sections demonstrated that the (100) boundary planes {(111)} have relative areas larger {smaller} than expected in a random distribution, and that the boundary plane distribution is inversely correlated to the boundary energy distribution.
  • Plasma sprayable grade zirconia powders doped with various mol% of yttria (0, 2, 3, 4, 6, 8 and 12 mol%) were synthesized by a chemical co-precipitation route. The coprecipitation conditions were adjusted such that the powders possessed good flowability in the as calcined condition and thus avoiding the agglomeration step like spray drying. Identical plasma spray parameters were used for plasma spraying all the powders on stainless steel plates. The powders and plasma sprayed coatings were characterized by X-ray diffractometry, Scanning Electron Microscopy and Raman spectroscopy. Zirconia powders are susceptible to phase transformations when subjected to very high temperatures duringmore » plasma spraying and XRD is insensitive to the presence of some non crystalline phases and hence Raman spectroscopy was used as an important tool. The microstructure of the plasma sprayed coatings showed a bimodal distribution containing fully melted and unmelted zones. The microhardness and wear resistance of the plasma sprayed coatings were determined. Among the plasma sprayed coatings, 3 mol% yttria stabilized zirconia coating containing pure tetragonal zirconia showed the highest wear resistance. - Research Highlights: {yields} Preparation plasma sprayable YSZ powders without any agglomeration process and plasma spraying {yields} Phase transformation studies of plasma sprayed YSZ coatings by XRD and Raman spectroscopy {yields} Microstructure of the plasma sprayed coatings exhibited bimodal distribution {yields} Plasma sprayed 3 mol% YSZ coating exhibited the highest wear resistance {yields} Higher wear resistance is due to the higher fracture toughness of tetragonal 3 mol% YSZ phase.« less
  • Thermal analysis was performed upon 3-mol%-yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) which had been doped with CuO using an aqueous adsorption technique. Cyclic differential thermal analysis (DTA) scans indicated that the CuO present on the powder surfaces first transforms to Cu{sub 2}O and then melts. The molten Cu{sub 2}O then reacts with yttria at the powder surfaces to form a new phase containing Y, Cu, and O. Because Y takes time to diffuse to the particle surfaces, the apparent melting point of this new phase appears at higher temperatures in initial DTA scans than in subsequent scans. Vaporization of the moltenmore » copper-oxide-rich phase at the temperatures studied causes a gradual shift in composition from Y{sub 2}Cu{sub 4}O{sub 5} to the less copper-rich Y{sub 2}Cu{sub 2}O{sub 5} phase. The presence of the Y{sub 2}Cu{sub 2}O{sub 5} phase in CuO-doped 3Y-TZP allows for previous sintering and superplasticity results to be explained.« less